1 //! Reading and writing of the rustc metadata for rlibs and dylibs
6 use rustc_codegen_ssa::METADATA_FILENAME;
7 use rustc_data_structures::memmap::Mmap;
8 use rustc_data_structures::owning_ref::OwningRef;
9 use rustc_data_structures::rustc_erase_owner;
10 use rustc_data_structures::sync::MetadataRef;
11 use rustc_middle::middle::cstore::{EncodedMetadata, MetadataLoader};
12 use rustc_middle::ty::TyCtxt;
13 use rustc_session::config;
14 use rustc_target::spec::Target;
16 use crate::backend::WriteMetadata;
18 pub(crate) struct CraneliftMetadataLoader;
20 fn load_metadata_with(
22 f: impl for<'a> FnOnce(&'a [u8]) -> Result<&'a [u8], String>,
23 ) -> Result<MetadataRef, String> {
24 let file = File::open(path).map_err(|e| format!("{:?}", e))?;
25 let data = unsafe { Mmap::map(file) }.map_err(|e| format!("{:?}", e))?;
26 let metadata = OwningRef::new(data).try_map(f)?;
27 return Ok(rustc_erase_owner!(metadata.map_owner_box()));
30 impl MetadataLoader for CraneliftMetadataLoader {
31 fn get_rlib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
32 load_metadata_with(path, |data| {
33 let archive = object::read::archive::ArchiveFile::parse(&*data)
34 .map_err(|e| format!("{:?}", e))?;
36 for entry_result in archive.members() {
37 let entry = entry_result.map_err(|e| format!("{:?}", e))?;
38 if entry.name() == METADATA_FILENAME.as_bytes() {
39 return Ok(entry.data());
43 Err("couldn't find metadata entry".to_string())
47 fn get_dylib_metadata(&self, _target: &Target, path: &Path) -> Result<MetadataRef, String> {
48 use object::{Object, ObjectSection};
50 load_metadata_with(path, |data| {
51 let file = object::File::parse(&data).map_err(|e| format!("parse: {:?}", e))?;
52 file.section_by_name(".rustc")
53 .ok_or("no .rustc section")?
55 .map_err(|e| format!("failed to read .rustc section: {:?}", e))
60 // Adapted from https://github.com/rust-lang/rust/blob/da573206f87b5510de4b0ee1a9c044127e409bd3/src/librustc_codegen_llvm/base.rs#L47-L112
61 pub(crate) fn write_metadata<P: WriteMetadata>(
64 ) -> EncodedMetadata {
65 use snap::write::FrameEncoder;
68 #[derive(PartialEq, Eq, PartialOrd, Ord)]
80 config::CrateType::Executable
81 | config::CrateType::Staticlib
82 | config::CrateType::Cdylib => MetadataKind::None,
84 config::CrateType::Rlib => MetadataKind::Uncompressed,
86 config::CrateType::Dylib | config::CrateType::ProcMacro => MetadataKind::Compressed,
89 .unwrap_or(MetadataKind::None);
91 if kind == MetadataKind::None {
92 return EncodedMetadata::new();
95 let metadata = tcx.encode_metadata();
96 if kind == MetadataKind::Uncompressed {
100 assert!(kind == MetadataKind::Compressed);
101 let mut compressed = tcx.metadata_encoding_version();
102 FrameEncoder::new(&mut compressed).write_all(&metadata.raw_data).unwrap();
104 product.add_rustc_section(
105 rustc_middle::middle::exported_symbols::metadata_symbol_name(tcx),
107 tcx.sess.target.is_like_osx,